1. Field of the Invention
The present invention relates to a method for removing voids in a ceramic substrate, and more particularly to a method including a chemical copper plating process after a sputtering titanium/copper step. The chemical copper plating step is able to successfully and electrically communicate both sides of the ceramic substrate so that when the copper pattern is formed on both sides of the ceramic substrate, communication is established.
2. Description of Related Art
Conventional leads of printed circuit ceramic substrates are made through a special metal mask in a vacuum environment by sputtering technology or evaporating technology. Because the leads are very thin and some oxide or nitride is mixed in the leads, it is necessary to use the ceramic substrate with high flatness, and an alumina material purity of 99.6%. Due to the above reason, the cost of the fabrication is very high.
For another conventional process of printed circuit ceramic substrates, the cost is low, but the flatness of the circuit is not satisfactory to reach the requirement of a high frequency circuit. The best width of the leads and width between each lead is 6 mil. For high frequency circuits, this process can not meet the requirements thereof. Furthermore, while preparing a ceramic substrate, titanium/copper sputtering is employed to communicate both sides of the substrate. However, because there are holes defined in the ceramic substrate and if the dimension of some of the holes is smaller than 100xcexc, the process of sputtering is not able to ensure that all the holes are covered with a layer of titanium/copper so that when the pattern is formed on the substrate, communication between both sides of the ceramic substrate is not satisfactory.
Therefore, it is an objective of the invention to provide an improved method to mitigate and/or obviate the aforementioned problems.
The primary objective of the present invention is to provide an improved method to satisfactorily establish communication between both sides of a ceramic substrate.
The method comprises defining holes in a ceramic substrate, sputtering titanium/copper film onto the ceramic substrate, chemical copper plating the ceramic substrate, forming a dry film onto the ceramic substrate, forming an image on the ceramic substrate, which consists of exposure and development, plating copper leads, plating nickel and gold, removing dry film, and etching titanium/copper.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.